Monday, August 25, 2008

APRS PHG circles

I've just installed an initial implementation of PHG (power-height-gain) circles on the live APRS map. They can be enabled by clicking on the new PHG icon in the top right corner. PHG circles are shown for APRS stations which are transmitting the PHG extension in their comment text.

The first click enables half-sized circles, which are supposed to resemble the reach of an APRS digipeater from a mobile user's point of view (small antenna at low height, lots of fading and multi-path propagation). The second click enables full-sized PHG circles which are calculated according to the APRS 1.0 specification, and might be quite optimistic for mobile users, but more realistic for connectivity between digipeaters and other installations with better antennas. Not surprisingly, the third click disables PHG circles again.

If you'd like to add the PHG extension to your digipeater configuration, please try the NashvilleAPRS PHG Calculator!

Update: There's a better PHG calculator at M0CYP's site which does PHGR - PHG with beacon Rate. aprs.fi doesn't display the rate yet, though.

21 comments:

Anonymous said...

Very cool!

VK5UJ said...

Awesome, thanks for the good work.

SW2HUI said...

Very usefull - thanks !!

SQ6NTI said...

Good to see this UI-View function finally implemented.
--
I also have one more question about something else: is it pssible to store station symbol history? Currently only the last icon is displayed no matter which period of history you choose.
--
Hessu, Kenwood has recently noticed your continued effort to keep this great service up and running. Take a look at these photos form Tokyo Ham Fair 2008:
http://aobajoke.no-ip.org/~ja7ude/HamFair2008/
Especially this one: http://aobajoke.no-ip.org/~ja7ude/HamFair2008/P1040936.JPG

oh7lzb said...

sq6nti: Ah, nice! Thanks for the link. I just had to add a new 'press' tag for publicity-related blog posts.

VE6SRV said...

Just a minor note... It's Power/Height/Gain, not Heading... however there is a directivity element in the PHG descriptor that gets missed in the label. To be fair, it really should be called PHGD.

oh7lzb said...

VE6SRV: Yeah, you're right about the TLA expansion. Thanks for the note.

VE6SRV said...

Further to directivity... any plans on adding support for this always overlooked element of the PHG equation?

The directivity element is supposed to offset the pattern by on third in the direction indicated. This is done to indicate a favoured direction or null.

I would suggest the use of a cardioid pattern in representing this offset value.

I am not aware of any APRS package that supports and displays this element even though it has been a part of the APRS PHG spec from day one.

Winston said...

how often do these circles update? What happens when a digi changes their PHG data?

oh7lzb said...

Winston: The PHG circles *should* update as soon as a new packet with a new PHG value is received (well, within a few seconds anyway). It could be that there is a bug somewhere, and it doesn't happen. Could you point me to a digipeater with a wrong PHG circle?

oh7lzb said...

VE6SRV: Yes, it would be nice to plot directivity in the PHG circles. Will have to refresh my math to modify the "plot a circle" function to plot something appropriate. :)

oh7lzb said...

PHG directivity has been implemented now, as a cardioid pattern.

VE6SRV said...

Sweet, works like a charm! apsr.fi/ve6srv-1 shows a pattern that offsets to the west, and gives a fairly good representation of the lack of RX towards the higher land east of me.

Wow, I even found 4 other stations in Western Canada that have a directivity selected!

Mark said...

Is there anyway to disable the text( vermogen 25W, antenne HAAT 3 m, gain 3 dBi omnidirectional, bereik 9.0 km) ??

oh7lzb said...

Mark,

Would you like to disable it for all PHG-enabled digipeaters or just your own? I can make it optional (selectable from the Preferences).

Mark said...

Make it a option to disable the line in the preferences ?

oh7lzb said...

Done! PHG can now be disabled from the preferences.

9A6AIV said...

9A6AIV:regards, for test purpose I set PHG in mobile sign.When I remove them they are stil on display.Is it possible to remove that information when you remove phg from beacon on mobile?Maybe it is the best way not to aloud phg info for mobile -9 sign.

oh7lzb said...

9A6AIV:

The SSIDs don't tell anything for sure, it's just a convention and recommendation that -9 *might* be a mobile. And there can be mobile digipeaters with a proper PHG. So no, we can't disable PHG for those.

There are a good bunch of digipeaters which save bandwidth on the APRS channel by only sending comment text in the beacon once every hour, or using 3 different comment texts sequentially, where only one comment text contains a PHG. So no, we can not delete the PHG data when we receive a packet with a PHG, those digis would only show the PHG 1/3rd of the time.

Maybe, if you send a PHG0000 (no power, no gain, and so on), it could be deleted.

9A6AIV said...

OK,thanks for quick reply.I try to send PHG000 now and before but info still remain on info baloon.No problem because I put mobile coverage :),so that info is still be up to date.

oh7lzb said...

9A6AIV: I found a bug in there, and fixed it now. PHG0000 should now work, I've tested that it deletes any existing old PHG data.